Common end closures for beer and beverage containers have a central panel that has a frangible panel (sometimes called a "tear panel", "opening panel", or "pour panel") defined by a score formed on the outer surface, the "consumer side", of the end closure. Popular "ecology" can ends are designed to provide a way of opening the end by fracturing the scored metal of the panel, while not allowing separation of any parts of the end. For example, the most common such beverage-container end has a tear panel that is retained to the end by a non-scored hinge region joining the tear panel to the reminder of the end, with a rivet to attach a leverage tab provided for opening the tear panel. This type of container end, typically called a "stay-on-tab" ("SOT") end has a tear panel that is defined by an incomplete circular-shaped score, with the non-scored segment serving as the retaining fragment of metal at the hinge-line of the displacement of the tear panel.
The container is typically a drawn and ironed metal can, usually constructed from a thin plate of aluminum. End closures for such containers are also typically constructed from a cut-edge of thin plate of aluminum or steel, formed into a blank end, and manufactured into a finished end by a process often referred to as end conversion, These ends are formed in the process of first forming a cut-edge of thin metal, forming a blank end from the cut-edge, and converting the blank into an end closure which may be seamed onto a container. Although not presently a popular alternative, such containers and/or ends may be constructed of plastic material, with similar construction of non-detachable parts provided for openability.
These types of "stay-on-tab" ecology container ends have been used for many years, with a retained tab and a tear panel of various different shapes and sizes. Throughout the use of such ends, manufacturers have sought to save the expense of the metal by down-gauging the metal of the ends and the tabs. However, because ends are used for containers with pressurized contents and are sometimes subject to pasteurization, there are conditions causing great stresses to the components of the end during pasteurization, transit and during opening by a user. These conditions limit the available gauge reduction of the end metal, and make it difficult to alter design characteristics of the end, such as by reducing metal gauge or the thickness of the metal residual in the score defining the tear panel.
Further, abuse during shipping, retail stocking and vending, due to rough handling of the filled containers, often causes problems with openability of the end. As an example of a problematic condition caused by handling abuse is the poor openability of a buckled container end. Due to dropping or abusive handling of filled containers, excessive pressure loads on regions of the end may cause a buckle of the end material. Such abuse, typically caused by dropping an upright container that is filled with carbonated fluid, results in a buckled end panel that deforms to form a bulge of metal of the panel.
The possibility of such buckling is a prevalent concern due to downgauging of the end material, pressurization of the container, pasteurizing filled containers, environmental conditions such as excessive heat, and rough handling of pallets or cases of filled containers. In a metal container end, the buckle appears as a deformation or bulge of the metal in a region of the end panel, a condition that adversely effects the users ability to open the end. Due to the geometry of the container and the ecology end panel, buckling of the end frequently is noticeable as a bulge of the end with a buckle in the 5:00 to 7:00 range of the end (with the middle of the tear panel positioned at 6:00). This type of buckled container end very often results in opening failure and resulting problems of a user trying to open the end.
Such a buckled end usually cannot be opened properly by the user. Instead, when the user lifts the tab and applies pressure on the tear panel with the tab nose, the score fractures at the wrong locations at the wrong time, usually resulting in a dramatic loss in leverage of the tab for opening the panel. In this situation, the tab is actuated against the tear panel by lifting the finger pull end of the tab, but the tab nose passes beyond the proximal peripheral edge of the tear panel, a condition often called "tuck under" of the tab.
The tab that tucks under is, therefore, fully lifted by the user, though the tear panel is still not fully opened. In this situation, the tear panel remains attaches by a segment of the score usually at about the 5:00 to 11:00 of the tear panel (defined with the tab nose being at about the 12:00 region of the tear panel). When this condition occurs, the user often tries to open the tear panel with something other than the tab, often by applying force by an object or the user's finger. However, such attempts at completing the opening sequence of the tear panel often causes fracture of the hinge of the tear panel, causing the tear panel to open entirely and become detached from the remainder of the end. When the user applies such force, a common result is for the hinge-line region of the metal, the non-scored fragment of metal that is intended to not fracture and to retain the tear panel, fails by fracturing along a non-specific tear of the metal away from the score. As a result, the tear panel is fully separated from the remainder of the end panel, and is usually pushed into the container. The fully detached tear panel then becomes a choking hazard or is otherwise a nuisance to the user and a potential pollutant. Therefore, there is a need for an end having design characteristics that prevents separation of the tear panel during user manipulation of ends with opening failure.
Further, with the more recent popular use of large-open ends, such problems with buckled ends is potentially greater. Because of the enlarged size and the shape of the opening panel (or tear panel), the score in certain regions of the large-open tear panel are more difficult to open by the tab leveraging against the tear panel. This is especially true for the region of the score which is in the 5:00 to 6:00 clock position. Therefore, large-opening ends may be difficult to open even when there is no noticeable sign of damage or buckle. Because of the additional force that may be required to open the large-opening tear panel with a tab, there may be more likelihood for non-specific tear of the metal away from the score. Also, because of the difficulty in opening the large-opening end, there is an increase in potential opening failure that results in "tuck under" of the tab. This type of opening failure also may result from the user opening the container too rapidly, not permitting proper venting of pressure from the container.
Because of these conditions, and the problem of potential tuck under of the tab and subsequent detachment of the tear panel when a buckled end results in opening failure and the user manipulates the end to open it, there is a need for an improved end structure that prevents or inhibits the total removal of the tear panel in the situation of an opening failure.